1. Field of the Invention
Embodiments of the present invention generally relate to electrostatic chucks for holding a substrate in a process environment.
2. Description of the Related Art
In substrate processing applications, chucks are used to hold a substrate to prevent movement or misalignment of the substrate during processing. Electrostatic chucks use electrostatic attraction forces to hold a substrate in position. The use of electrostatic chucks has gained wide acceptance due to their advantages over mechanical and vacuum chucks, such as the reduction of stress related cracking in the substrate, the reduction of contamination in the processing chamber, and the ability to retain a substrate in a low vacuum environment.
A typical electrostatic chuck includes an electrically conductive electrode embedded within an electrical insulator. A voltage source electrically biases the substrate with respect to the electrode. The insulator prevents the flow of electrons therethrough, causing opposing electrostatic charges to accumulate in the substrate and in the electrode. Thus, an electrostatic force is generated to attract and hold the substrate onto the chuck.
A common electrostatic chuck is a multilayered structure fabricated using polyimide for the insulating layers sandwiching a copper electrode. Polyimide is a thermosetting material that has desirable properties such as high temperature stability (relative to other organic polymers), good dielectric behavior, and good mechanical properties. However, the use of polyimide to insulate the electrode limits the lifetime of the chuck in certain substrate fabrication processes. Polyimide and similar polymers have low erosion resistance for certain process gases and plasmas. Oxygen-containing gases and plasmas, which are used for a variety of substrate processing operations, are particularly detrimental to the polyimide layers on the electrostatic chuck. During these processes, the insulator can be eroded by the process gas and the resultant exposure of the electrode results in failure of the chuck during processing and loss of the entire substrate at a significant cost.
In addition, when a substrate breaks or chips to form fragments having sharp edges, the substrate fragments can easily puncture the polyimide film exposing the electrode of the chuck. Substrate fragments can also be transferred to the polyimide film from the substrate backside. Exposure of the electrode at even a single pinhole in the insulator can cause arcing between the electrode and plasma, and require replacement of the entire chuck.
Further, the process of manufacturing the aforementioned electrostatic chuck requires the use of pressure or heat sensitive adhesives as well as a laborious circuit buildup. For instance, a polyimide film having an electrically conductive copper layer may be supplied. The copper layer may be etched, routed, or milled to form the electrode. After etching, a second polyimide film layer may be adhered over the electrode layer using a pressure or heat sensitive adhesive. The multilayer stack is then adhered to the base of the chuck using a pressure or temperature sensitive adhesive. This process is not only complicated, requiring many steps and extended fabrication time, but the adhesive layers may also be detrimentally affected by process conditions within certain process chambers. This may result in delamination of the layers, requiring replacement of the entire chuck.
Therefore, a need exists for an improved electrostatic chuck and a simplified method of manufacturing the same.